[ncl-talk] Rossby wave filtering

[Wickramage Chathurika]

Hello,
I want to filter Rossby waves from zonal ocean velocities. can I use the function "kf_filter" and can I use zonal velocities to filter Rossby waves in ocean? I have tried to do and the script is below;

fi=addfile("/mnt/e/data/HYCOM/u/2004_june.nc","r")vname=getfilevarnames(fi)print(vname)
oc=fi->WATER_U(:,{0:200},{5.5},{76:86})printVarSummary(oc)
t=fi->TIMEprintMinMax(t, False)
obsPerDay=8tMin=731734tMax=731763.875kMin = 1kMax = 14hMin=5hMax=60waveName="Kelvin"
x=oc(:,{40},:)x!0="time"x!1="lon"
kf=kf_filter(x(:,:), obsPerDay, tMin, tMax, kMin, kMax, hMin, hMax, waveName)
printMinMax(kf, False)
and the output information is below;
Variable: vnameType: stringTotal Size: 64 bytes            8 valuesNumber of Dimensions: 1Dimensions and sizes:   [8]Coordinates:(0)     LON2876_3501(1)     LON2876_3501_bnds(2)     LAT876_1251(3)     LAT876_1251_bnds(4)     LEV1_28(5)     LEV1_28_bnds(6)     TIME(7)     WATER_U
Variable: ocType: floatTotal Size: 2782080 bytes            695520 valuesNumber of Dimensions: 3Dimensions and sizes:   [TIME | 240] x [LEV1_28 | 23] x [LON2876_3501 | 126]Coordinates:            TIME: [731734..731763.875]            LEV1_28: [   0.. 200]            LON2876_3501: [  76..  86]Number Of Attributes: 5  LAT876_1251 : 5.51999998093  missing_value :       -30000  _FillValue :  -30000  long_name :   eastward water velocity [m/s]  history :     From 3hourly(0)     time (days since 0001-01-01 00:00:00) : min=731734   max=731763.875(0)     eastward water velocity [m/s] : min=-0.00192383   max=0.00160925
P.S; When I try to filter "Mixed Rossby-Gravity" waves, all output results were "zero". In above script, I have filtered "Kelvin" waves. I really appreciate if anyone could help me to figure out this and any suggestion about how to filter "Rossby waves" is appreciated in advance.

Kind Regard;Chathu

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